Naive-derived CD8+ T cells possess a superior capacity to engraft, expand, and mediate tumor regression following adoptive transfer compared to memory-derived T cells. However, whether the antigen-experienced subsets may directly influence naive cell differentiation is unknown. We show that human and mouse memory lymphocytes caused naive T cells to undergo augmented differentiation following priming both in vitro and in vivo. This process, which we term precocious differentiation, resulted in the accelerated functional, transcriptional, and metabolic differentiation of TN-derived progeny. Precocious differentiation was mediated by non-apoptotic Fas signaling delivered by memory cells to naive cells resulting in Akt-driven cellular differentiation. Consequently, blockade of Fas-signaling prevented TMem-induced precocious differentiation and preserved the antitumor efficacy of TN-derived cells while induction of Fas-signaling in the absence of TMem enhanced differentiation and impaired antitumor immunity. Collectively, our results reveal that unleashing the therapeutic potential of TN-derived cells requires disruption of cellular communication with TMem, a finding with significant implications for the design and execution of T cell therapy clinical trials.